I been working on a small project at home. I have a mobile robot with 2 servos operating the wheels and 6 others operating an arm, making it a total of 8 servos. I'm currently using Arduino Mega and an external power supply, a modified ATX power supply (5V 30A). I have a battery from a previous R/C car project, 7.2V 4500mAh. I would like to use this battery to power the robot. I've tried connecting it directly but the servos do not switch on. I get a big voltage drop and current drop, as many of you figured out already. I thought if I made a simple voltage follower it would work, but didn't. How else can I power these servos without buying a Servo Controller. I would like to make a circuit with parts that can easily be found locally. Any help that can be offered, would be great.

Are your servos rated for 7.2v operation? Many are not. If not, you will need some type of voltage regulator.

I power 18 servos off of a higher voltage battery and use a voltage regulator from http://www.dimensionengineering.com/I got the SWADJ3, which lets me cut select the output voltage, and it handles enough current for my needs.

As for the physical arrangement, I bought a prototyping shield and some pin headers.http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1265626147/6#6

Vince, I like what you did with the voltage regulator. But can you give me a list of the parts you used, the voltage regulator, battery, and the small circuit board switch(what does this do? do I need it?). Also, the pictures are great but are a bit fuzzy to see the connections in detail. Could you give me a quick short summary how you connected these devices.

Pololu Pushbutton Power Switch SVhttp://www.pololu.com/catalog/product/750This is a power switch that replaces a mechanical switch.

Small breadboardhttp://www.pololu.com/catalog/product/1490

Various headers#1065 #966 #965

Power block#830 Although this comes out of the bread board fairly easily.

I also got wire kits#313 Elenco JW-350 350-Piece Wire Kit

Dimension EngineeringVoltage regulatorhttp://www.dimensionengineering.com/DE-SWADJ3.htmThey have many different models to choose from, with widely ranging capacities. This model works for my 18 servos - 12 are standard sized analog, and 6 are standard sized digital.